Abstract

Apoptosis is an inevitable process during development and is evident in the formation of articular cartilage and endochondral ossification of growth plate. Mesenchymal stem cells (MSCs) can serve as alternative sources for cell therapy in focal chondral lesions or diffuse osteoarthritis. But there are few, if any, studies investigating apoptosis during chondrogenesis by MSCs. The aim of this study was to find the better condition to prevent apoptosis during chondrogenesis by MSCs. Apoptosis were evaluated in MSCs induced in different chondrogenic media by the use of Annexin V, TUNEL staining, lysosomal labeling with lysotracker and immunostaining of apoptotic markers. We found apparent apoptosis was demonstrated by Annexin V, TUNEL staining and lysosomal labeling during chondrogenesis. Meanwhile, the degree of apoptosis was related to the reagents of the defined chondrogenic medium. Adding serum in medium increased apoptosis, however, TGF-β1 inhibited apoptosis. The apoptosis was associated with the activation of caspase-3, the increase in the Bax/Bcl-2 ratio, the loss of lysosomal integrity, and the increase of PARP-cleavage. Pro-inflammatory cytokines, IL-1α, IL-1β and TNFα did not induce any increase in apoptosis. Interestingly, the inhibition of apoptosis by serum free medium supplemented with ITS was also associated with an increase in the expression of type II collagen, and a decrease in the expression of type X collagen, Runx2, and other osteogenic genes, while TGF-β1 increased the expression of Sox9, type II and type X collagen and decreased the expression of osteogenic genes. These data suggest apoptosis occurs during chondrogenesis by MSCs by cell death intrinsic pathway activation and this process may be modulated by culture conditions.

Keywords

Apoptosis Chondrogenesis Mesenchymal stem cells TGF-beta1 Serum

Ling-Lan Chen and Pei-Yin Kuo are equal contributors.

Electronic supplementary material

The online version of this article (doi:10.1007/s10495-009-0431-x) contains supplementary material, which is available to authorized users.

Notes

Acknowledgments

Grants supported by Veterans General Hospital-Taipei (R92-001-6, Stem Cell Grant-supported by HealthBanks Biotech); National Science Council (94-2314-B-075-019; 97-2627-B-010-003) and National Yang-Ming University, Ministry of Education.

Conflict of interest

The authors have no conflict of interest to disclose with regard to the subject matter of this present manuscript.